1. Technical Field
The invention concerns improved trick mode playback, and more particularly to improvements in the trick mode playback of audio programming associated with a video segment played back at other than normal speed.
2. Description of the Related Art
DVD trick modes can include speedup or slowdown of normal playback to either search for a specific location on the disc or to look at details of a clip that would normally be missed at normal speed. By convention, normal playback speed can be denoted as 1×. Both audio and video trick modes are possible and both can be found on commercially available DVD players. However, conventional methods for playback of audio at fast or slow speed have proved to be problematic. The advancement of digital signal processors and especially audio digital signal processors that are used in currently available products have created the possibility for more sophisticated real-time processing for improved audio trick modes.
One problem with the use of video trick modes concerns the treatment of audio corresponding to a playback video segment. For example, when a user speeds up or slows down a displayed video segment, the corresponding audio segment that is played back can be distorted. Typically, audio samples in the audio segment can be shifted to higher frequencies during a fast trick mode, and lower frequencies during a slow trick mode. The fast trick modes that increase the playback speed by a factor of between about 1.5 to 3 times as compared to normal playback will tend to cause human speech to sound higher in pitch. This higher pitched audio playback, the chipmunk effect, can be annoying and in many instances may be unintelligible for a listener. Conversely, slow frequency trick modes can produce a low frequency wobble that may be understandable but not aurally pleasing.
In order to obtain the most useful audio playback during video trick modes as described herein, it is also necessary to consider the nature of the particular trick mode. For example, while it may be possible to utilize various techniques to provide intelligible audio for 1.5× or 2× trick modes, such techniques may provide unsatisfactory results when the trick mode involves playback at 5× or 10×. At such high rate playback speeds, any attempt to play back an audio soundtrack synchronized with the video may result in unintelligible speech due to the very rapid rate at which words would need to be presented.
To avoid hearing various types of audio artifacts that can be caused by DVD trick modes, conventional DVD players will often mute the audio during video trick modes. However, this is not an entirely satisfactory solution as the audio may be of interest in such modes. Accordingly, it would be advantageous if a DVD player could playback audio in a manner that overcomes the limitations of the prior art and achieve a desirable and aurally pleasant playback of audio during video trick modes.